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How to adjust your baby's age for sleep

Updated: Jul 9, 2023

First things first: Does your baby have an adjusted age?


Depends on who you ask and what article you are reading. Typically, babies are considered full term at 40 weeks. The 40 weeks is an average of 37 & 42 weeks. If your baby was born somewhere inside this gestation timeline, they can be considered "full term".


When adjusting the age of your baby, a rule of thumb can be: If your baby was born full-term, but just 1-3 weeks early, you can use their actual age from their birthdate.


If your baby was born more than 4 weeks before their due date, you can adjust their age from their due date; taking into consideration that your baby may be closer to the "full term" 37 weeks or "full-term" 40 weeks depending on how early they were born.


For example: if your baby was born at 36 weeks, you may wonder if your baby is considered 1 week early or 4 weeks early.


Technically, they are not considered full term, therefore you can consult your child's pediatrician for any adjustment of age. It may be confusing, and that's because it is.


Even this article by HealthyChildren.org states that to calculate the corrected age of a baby, to subtract from 40 weeks, and then they go on to say that 39 weeks is considered full term. Okay, what?


How to adjust sleep for a premature baby


Babies born early may not be able to handle the typical wake windows that you see suggested. Once out of the newborn stage and your baby isn't sleeping the entire day, take notice of their most alert time throughout the day and keep watch of how long it lasts.


For many babies, they become more alert after the 6-8 week growth spurt.


If your child is still showing newborn tendencies and sleeping around the clock, this may be in indicator that their sleep windows will need to follow an adjusted age. This may look like shaving 30-45 minutes off the wake window for your baby's actual age.


Prematurity & wake windows


This graphic is a good one to save as it shows suggested wake windows by age. The age is calculated for a baby born between 37 & 42 weeks. If you notice your child's sleep does not line up, you may want to be more conservative with their wake windows.

Baby wake windows by age

When do premature babies sleep through the night?


Sleeping through the night can mean long stretches of sleep on either side of a feeding, for example. It's best to ask your child's pediatrician when your baby can be weaned or if they must still be woken to eat at night.


In the early stages, your pediatrician will be keeping a close eye on their weights and growth chart to make an accurate suggestion for you when the time comes.


Babies can drop their middle of the night feed early on, or keep a feed closer to 1 year old. To ensure your baby is getting adequate calories during the day, I suggest at least 5 full feeds in the daytime from newborn until about 6-8 months old.


Premature babies can sleep through on the same timeline as a full-term baby if they are growing well, and again, you have permission to wean.


What should premature babies sleep in?


In the United States, the AAP recommends baby to sleep on a flat surface such as a crib or bassinet, without any loose blankets or clothing and on their back.


The use of a swaddle for a premature baby can be really helpful to mimic the womb and help baby adjust to the big world. Note: discontinue swaddling at 3 months old or at first signs of rolling. In addition to a swaddle for your premie baby, use a sound machine for all sleep.


The use of a white noise machine can also help calm baby as it mimics the sounds in the womb and can help trigger baby's calming reflex.


Remember that it's white/pink/brown noise that's suggested for sleep, not raindrops or ocean sounds!


Sleep training a premature baby


When is the right time to start sleep training if baby was born early?


Every baby is different, so this may mean baby sleeps long stretches of sleep before and after 4 months of age, or that they never, ever slept more than 2-3 hours and the 4-month regression wasn't noticed because baby's sleep was already terrible.


I can attest to the latter scenario with my twins. Sleep training a premature baby can look similar to that of a full-term baby. Your baby can start sleeping better with any of the popular sleep training methods like chair method, or leave and check sleep training method.


Want to get a head start on laying an independent sleep foundation?

You'll want this guide for twins and this guide for a singleton!


What age can you sleep train a premature baby?


Once you notice your baby is having wake windows of about 90-minutes to 2 hours long, is a milestone I like to look for when deciding if a baby is ready.


They will likely be taking 4 naps per day with indicators they are ready to go down to 3 naps soon.


We also don't have to factor in weight or calorie intake, because sleep training, especially at 4 months old, doesn't necessarily mean night weaning. I hear the magic '16-weeks' as being the official time you can start, but I've helped twins, for example, who weren't yet 16 weeks adjusted but they did great because parents were super ready to get onto a schedule and sleep routine.


What age can you STOP adjusting your baby's age for sleep?


Again, it's a little fuzzy, but another rule of thumb is that you can stop adjusting your baby's age for sleep around 6-8 months, or when baby is transitioned to a 2 nap per day, clocked schedule.


Then, there is the question about whether or not you have a high sleep needs or low sleep needs baby.


This graphic below can shed some light on the averages and may tell you if your baby is sleeping more or less than the averages here.


*These averages were provided by the National Sleep Foundation.

Baby sleep totals by age
Average sleep needs by age

I hope this article has helped make a little more sense about a question you may ask yourself a lot.


Remember that each baby is different, and even fraternal and identical twins can have slightly different sleep needs. All feeding advice for your baby(s) should be directed to your child's pediatrician.


Lindsay Loring is the author of this article.


She is a mom to twins and certified pediatric sleep consultant in the St. Louis, MO metro area.

She is the owner of Tweet Dreamzz Sleep Consulting.

Book a call with Lindsay to find out how better sleep can happen for your baby.


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